Modernisation of the US Army's helicopter fleet is built around powerplants designed 30 to 40 or more years ago. While growth versions of these engines will meet the army's power requirements for the foreseeable future, they fall short of the fuel consumption, power-to-weight and cost goals that have been the target of the service's research efforts for the past decade.

Lack of funding has prevented the US Army from launching de­v­­­­­­­elop­ment of a new-centreline engine, but the service has continued to fund R&D to mature technology for insertion in existing engines and to provide the foundation for future powerplants. The longest running of these research efforts, the Joint Turbine Advanced Gas Generator (JTAGG) programme, is drawing to a close.

Part of the successful US Department of Defense-led Integrated High Performance Turbine Engine Technology (IHPTET) programme begun in 1988, JTAGG will complete its second phase this year and its third and final phase next year – but with no signs of an all-new engine.

"We are getting to the end of JTAGG II," says Ron Rich, director, advanced technology development, Honeywell Engine Systems & Services. "We are preparing for final testing of a core engine meeting the Phase 2 goals of a 30% reduction in sfc [specific fuel consumption] and 70% increase in the power-to-weight."

Testing of the final build of Honeywell's XTC56 core is scheduled for year-end. "Then we are finished," says Rich. JTAGG II is aimed at a 3,000shp (2,240kW) turboshaft, which the army plans to develop under the Improved Turbine Engine Programme (ITEP). But the service does not have sufficient funds to launch development of the ITEP, which would power growth versions of the Boeing AH-64 and Sikorksy UH-60. Instead, the technology is being inserted into existing engines. "JTAGG II will be successful whether or not ITEP comes along," says Rich.

Honeywell, this time teamed with General Electric, is getting ready to test the first core under Phase 3 of JTAGG, which has as its goals a 40% reduction in specific fuel consumption (sfc), 120% increase in power-to-weight and 35% savings in unit and operating costs. "Tests will start later this quarter or early in the summer," says Rich.

Tests will continue through next year, with later builds of the XTC97 core, as Honeywell and GE work towards meeting the Phase 3 goals. JTAGG III is aimed at a 10,000shp-class turboshaft – originally to power the US Army's planned Advanced Manoeuvre Transport, which has been superseded by DoD-level efforts to launch development of a joint vertical heavylift aircraft.

Meanwhile, under the DoD's follow-on to the IHPTET, the Versatile Affordable Advanced Turbine Engines programme, the US Army is funding work on the Small Heavy Fuel Engine (SHFE) – a 700shp-class turboshaft that could power light helicopters and unmanned air vehicles. Honeywell won the cost-sharing contract to build and test the SHFE in 2003.

The company has run component and compressor rigs, with a combustor rig to follow "in the next couple of months" and the core engine to run by year-end. Testing of the full engine is to begin early next year and will continue into 2007, culminating in a third and final build demonstrating the goals of a 20% reduction in sfc, 50% increase in power-to-weight and 35% life-cycle cost savings.

Honeywell is confident the SHFE will lead to a new engine, because the technology is scalable between 500shp and 1,500shp and has multiple applications, powering light commercial helicopters as well as armed scouts and UAVs. "It has applications that are commercial and military, manned and unmanned, aviation and ground," says Rich. It remains to seen whether the US Army can find – and fund – an application.


Source: Flight International